Is The New Zerodha 20 Market Depth Tick By Tick Or Is It Just Snapshot

Is The New Zerodha 20 Market Depth Tick By Tick Or Is It Just Snapshot ?
And When Will It Comes To Kite API.

Tick by tick data delivery to a retail user can’t be done due to the bandwidth limitations in internet connections

Hence, 20 Market Depth data is a snapshot and not tick by tick